This invention relates to heat exchangers of the type formed of stacked plates, wherein the plates have raised peripheral flanges that co-operate to form an enclosure for the passage of heat exchange fluids between the plates.
The most common kind of plate type heat exchangers produced in the past have been made of spaced-apart stacked pairs of plates where the plate pairs define internal flow passages therein. Expanded metal turbulizers are often located in the internal flow passages to increase turbulence and heat transfer efficiency. The plates normally have inlet and outlet openings that are aligned in the stacked plate pairs to allow for the flow of one heat exchange fluid through all of the plate pairs. A second heat exchange fluid passes between the plate pairs, and often an enclosure or casing is used to contain the plate pairs and cause the second heat exchange fluid to pass between the plate pairs.
In order to eliminate the enclosure or casing, it has been proposed to provide the plates with peripheral flanges that not only close the peripheral edges of the plate pairs, but also close the peripheral spaces between the plate pairs. One method of doing this is to use plates that have a raised peripheral flange on one side of the plate and a raised peripheral ridge on the other side of the plate. Examples of this type of heat exchanger are shown in U.S. Pat. No. 3,240,268 issued to F. D. Armes and U.S. Pat. No. 4,327,802 issued to Richard P. Beldam.
A difficulty with the self-enclosing plate-type heat exchangers produced in the past, however, is that the peripheral flanges and ridges form inherent peripheral flow channels that act as short-circuits inside and between the plate pairs, and this reduces the heat exchange efficiency of these types of heat exchangers.
In the present invention, portions of the expanded metal turbulizers are crimped closed to act as barriers to reduce short-circuit flow and to improve the flow distribution between the plates and the overall heat exchange efficiency of the heat exchangers.
According to the invention, there is provided a plate type heat exchanger comprising first and second plates, each plate including a planar central portion, a first pair of spaced-apart bosses extending from one side of the planar central portion, and a second pair of spaced-apart bosses extending from the opposite side of the planar central portion. The bosses each have an inner peripheral edge portion and an outer peripheral edge portion defining a fluid port. A continuous ridge encircles the inner peripheral edge portions of at least the first pair of bosses and extends from the planar central portion in the same direction and equidistantly with the outer peripheral edge portions of the second pair of bosses. Each plate includes a raised peripheral flange extending from the planar central portion in the same direction and equidistantly with the outer peripheral edge portions of the first pair of bosses. The first and second plates are juxtaposed so that one of: the continuous ridges are engaged and the plate peripheral flanges are engaged; thereby defining a first flow chamber between the engaged ridges or peripheral flanges, with the fluid ports in one of said pairs of spaced-apart bosses forming an inlet and outlet to the first flow chamber, and the chamber defining a flow path between the inlet and outlet. The fluid ports in the respective first and second pairs of spaced-apart bosses are in registration. Also, an expanded metal turbulizer is located between the first and second plate planar central portions. The turbulizer includes a crimped portion located in the flow path to reduce short-circuit flow between the inlet and the outlet.